Aortic Coarctation

Coarctation of the aorta is a narrowing of the aorta, the main blood vessel carrying oxygen-rich blood from the left ventricle of the heart to all of the organs of the body.

Coarctation occurs most commonly in a short segment of the aorta just beyond where the arteries to the head and arms take off, as the aorta arches inferiorly toward the chest and abdomen.

This portion of the aorta is called the "juxtaductal" aorta, or the part near where the ductus arteriosus attaches. It is also called the aortic isthmus.

The ductus arteriosus is a blood vessel that is normally present in a fetus and has special tissue in its wall that causes it to close in the first hours or days of life. Coarctation may be caused by the presence of extra ductal tissue extending into the adjacent aorta which results in aortic narrowing as the ductal tissue contracts.

In babies with coarctation, the aortic arch may also be small (hypoplastic). Coarctation may also occur with other cardiac defects, typically involving the left side of the heart. The defects most commonly seen with coarctation are bicuspid aortic valve and
ventricular septal defect . Coarctation may also be seen as a part of more complex
single ventricle heart defects .

Coarctation of the aorta is common in some patients with chromosomal abnormalities, such as Turner's syndrome.

In the presence of a coarctation, the left ventricle has to work harder, since it must generate a higher pressure than normal to force blood through the narrow segment of aorta to the lower part of the body.

If the narrowing is very severe, the ventricle may not be strong enough to perform this extra work, resulting in
congestive heart failure or inadequate blood flow to the organs of the body.

Coarctation of the aorta is present from birth. The age at which coarctation is detected depends on the severity of the narrowing.

In approximately 25 percent of cases of isolated coarctation, the narrowing is severe enough to cause symptoms in the first days of life when the ductus arteriosus closes. When the ductus arteriosus closes, the left ventricle must suddenly pump against much higher resistance and this can lead to heart failure and shock. Because these newborns are well until the ductus arteriosus closes, symptoms appear rapidly and are often severe.

In patients who don’t develop heart failure as newborns, coarctation may not be detected until the child is several years old. In these older patients, coarctation is often first suspected because of a heart murmur or high blood pressure.

Coarctation is suspected when the physician is unable to feel pulses in a child’s legs. High blood pressure in the arms (but not the legs) may be detected. A heart murmur is usually present and may be loudest in the back (where the aorta is located).

The diagnosis of coarctation is usually confirmed with echocardiography, which can define the anatomy of the aorta and evaluate for other cardiac anomalies that may also be present. Occasionally other tests, such as a cardiac MRI or CT scan, may be used to document the presence of a coarctation.

In a critically ill newborn, the goals of management are to improve ventricular function and restore blood flow to the lower body. A continuous intravenous medication, prostaglandin (PGE-1), is used to open the ductus arteriosus (and maintain it in an open state) allowing blood flow to the body beyond the coarctation. It is also often necessary to begin intravenous medications that improve the contraction of the heart muscle. Babies will almost always need to be placed on a ventilator before surgery.

In symptomatic newborns with coarctation, surgical repair is usually done on an urgent basis following initial stabilization. Rarely, an infant will not improve with medical therapy and surgery must proceed before the infant has been stabilized.

There a number of surgical techniques to repair coarctation. A common repair involves resection (removal) of the narrowed area with anastomosis (reconnection) of the two ends to each other. This repair is called an end-to-end anastomosis. Another common repair involves taking the aorta after the area of narrowing and anastomosing it with the ascending aorta. This type of repair is called an arch advancement and is done when there is more diffuse hypoplasia. Less commonly, the narrowing may be opened with a patch, or a portion of an artery may be used as a flap to expand the area (called a subclavian flap aortoplasty).

Because older children may have minimal symptoms, coarctation repair is typically planned electively. Surgical repair is most commonly performed with resection of the narrowed segment and end-to-end reconnection.

In older children, an alternative to surgery may be catheter-based therapy. In selected cases, the area of narrowing may be dilated with a balloon. In some patients the coarctation can be treated very effectively with the placement of a metal stent. Because stents don’t grow, this therapy is typically used in older, larger patients. The availability of covered stents, investigational in the United States, will probably enhance the safety and effectiveness of coarctation stenting in the future.

In order to repair coarctation surgically, clamps must be placed on the aorta, briefly interrupting blood flow to downstream areas. Potential complications of surgery, although uncommon in children, are damage to downstream organs, particularly the kidneys or the spinal cord.

Recurrence of coarctation at the site of surgical or balloon treatment is possible, even years following treatment. The rate of restenosis is highest among newborns, occurring in 10 percent to 20 percent of patients. The rate of recurrent coarctation after surgical repair decreases in older children, approaching zero by age 3. While some patients with recurrent coarctation may require repeat surgery, the majority of cases can be managed with balloon dilation or stenting.

Another concern after coarctation repair is hypertension (high blood pressure). While this is rarely seen in infants, most older children have unusually high blood pressure immediately following surgery that is treated with intravenous medication. Frequently, children will be sent home on medication to treat high blood pressure.

Although blood pressure will return to normal in many children (allowing medication to be discontinued), long-term or late hypertension may occur in some patients, requiring long-term treatment.

Long-term follow-up with a cardiologist is very important for children after coarctation treatment to diagnose late problems of restenosis or hypertension. Follow-up visits include a physical exam with blood pressure measurements in both the arms and legs. Periodic electrocardiograms and echocardiograms may also be performed. In older and larger patients cardiac MRI or CT scans may be obtained intermittently to better evaluate the repaired aorta. Long-term cardiology follow-up is also important for any associated cardiac lesions (such as bicuspid aortic valve) that may be present.

Most adults born with aortic coarctation will have had repair in childhood. This repair may have been surgical or performed in the cardiac catheterization laboratory using a balloon or stent. These patients require lifelong periodic monitoring by a congenital heart specialist for number of reasons.

First, the narrowing of the aorta may recur, or may not have been completely repaired at all. Secondly, aneurysms can form either at the site of repair or elsewhere in the aorta. These need to be excluded by either MRI studies or CT studies. Third, patients who have had aortic coarctation repair have a high frequency of high blood pressure that needs treatment. Sometimes the treatment is with medications, sometimes with a stent or other procedure. Next, patients who have a history of aortic coarctation usually have a bicuspid aortic valve. This valve may or may not malfunction over time. Patients who have such valves also have a tendency to aneurysms of their ascending aorta.

So while we expect patients with a repaired aortic coarctation to do well, additional treatment of one form or another may be required in order for them to protect their long-term health.